So many "experts" get hung up on having every gun under the sun to defend themselves. They feel they must have brand X or Y with these certain features and in this color with exactly the caliber they say. What a bunch of hooey. There are a few things you do NEED to have.
1. A functioning firearm
2. Cleaning kit for said firearm
3. Ammunition for the same firearm.
4. The skill to use it.
For a long time I've helped out from time to time at a gun shop that prides itself on making a customer for life out of the people who tread through the door. Over the last 17 years of hanging out there and buying hundreds of guns from the guys there, I've found many words of wisdom. The first of those being, beware the man with one gun, he more than likely knows how to use it.
Don't get hung up on which brand is the best or what sight system is optimal for certain conditions. The gun you have in your hand is the one that can get you out of trouble. The 16 in the safe are useless when you can't get to them.
Characteristics of a good firearm.
1. Functional 100% of the time
2. Sights you can see
3. Easy to use
4. Easy to reload
5. Proper weight and length for you to use in most environments
6. A caliber that is readily available
7. Accurate enough for your needs
If the gun won't work unless you jiggle the hammer a little, it's useless. If you can't aim it, why bother. If it's a single shot bolt action, you might have trouble with multiple targets. The L82A1 Barrett is a bad machine, but can you carry it in the woods or along your property line? There are a bunch of really cool rifles out there in exotic calibers, but will that be any use to you if you can't feed it or afford to feed it.? Accurate enough means just that, as long as you can hit a dirtbag sized target at the ranges you will more than likely engage at, you're good to go.
Being a certified gun nut, I have more than I need. I have multiple calibers and multiple platforms for engagement from point blank out to 1500 meters. I'm not saying everyone needs that, but I sure like mine. All but a couple of my guns are common calibers. 22lr, 12ga, 380acp, 9mm, 38spl/357mag, 40SW, 45acp, 223 and 308. I do have a couple odd balls. A 10mm and 300Win Mag. Why? Because I can. Common calibers ensure you can more than likely scrounge ammo in any situation. The 2 uncommon calibers I have are the ones I CAN get ammo for these days. Scary, right? 10mm ammo is going for $50 a box now and 300 WM is about the same, but it's available if I was out. I can't say the same for common calibers.
What would I consider a good "Stash" of firearms?
A carbine in a common caliber. 223/5.56, 7.62x39, 308, 30-06
A pistol that can be carried concealed in a caliber above 380acp and below 41 magnum.
A pocket pistol in 22mag, 32, 380 or 9mm.
A bolt action scoped center fire rifle in a common hunting caliber.
A collection like this would have an arm available to fit the needs of most people in a serious need to defend themselves or feed themselves. I will say this though, a man with a 10/22 rifle and home field advantage could put a hurting on some well trained operators.
There is no replacement for trigger time. The more you shoot the better you will become. Training will speed up your abilities as well. I really can't stress that enough. A good instructor can shorten your learning curve by years. They can short cut you past all the mistakes people make in the beginning and allow you to focus on proper techniques and build confidence in your abilities. If you think about it, it's the cheapest way to become a better shooter. You can shoot 10k rounds a year and get very good, or take a few classes at 500 a pop and be thousands of dollars ahead monetarily and months ahead as well.
Any machine that isn't used will fall into disrepair. Practice!
A large stock of ammo is secondary to being able to utilize the firearm. If you have stashed up thousands of rounds of ammo, but haven't trained because you wanted to hoard it, you're behind. Have a decent stash, but concentrate on keeping your skills sharp. That ammo will only do the next guy good if you lose your first gun fight because you're rusty.
In closing, I'll offer a last bit of sage advice. If you find yourself in a fair gunfight, your tactics suck. If I'm forced to defend my life, I'd prefer to take the shot at 600 yards with a high powered rifle. The less danger you put yourself in the better your chances of defeating the opposition.